This disclosure relates to a process for selecting an antenna in a wireless communication system having a plurality of antennas. In particular, the present invention is designed to select an antenna that provides superior transmission and reception quality using a singular quality indicator that reflects a plurality of quality parameters.
In wireless communication systems, incoming signals may experience time dispersion and fading which is known as multipath interference. Multipath interference is caused by the destructive interference of radio waves arriving at an antenna through diverse paths. In wireless technology, the phase differences of signals arriving at a receiver through diverse paths can cause distortion that detracts from signal quality. Conventional wireless technology utilizes spatial diversity to minimize multipath interference. A wireless network commonly includes more than one antenna positioned such that the signals received by the antennas are not correlated.
When more than one antenna is used in a wireless system, a protocol is employed for antenna selection. Normally, antenna selection is based on a received signal quality assessment. In some wireless communication systems, such as Time Division Duplex (TDD), uplink and downlink channels are coupled. The assimilation of uplink and downlink channels transmitted in a common frequency separated only in time means that both channels suffer from the constructive and destructive reflections of signals arriving at an antenna through diverse paths. Accordingly, a process that minimizes multipath interference, such as spatial diversity, benefits the uplink and downlink channels together as they are transmitted and received in a single frequency.
In Frequency Time Division Duplex (FTDD), full duplex communication is established by separating the uplink and downlink channels in frequency. This means that an antenna transmitting a high quality signal at an uplink frequency will not necessarily receive a high quality signal at a downlink frequency. Furthermore, as a receiver or transmitter moves from one location to another, the phase relationship between diverse signals changes relative to their motion which may cause one frequency to suffer from a different set of losses and reflections than another frequency. Accordingly, the multipath interference that comes and goes from the scattering of signals from obstacles in a signal""s path is different under a Time Division Multiple Access (TDMA)/TDD format then under a TDMA/FTDD format.
The co-existence of variety in TDMA wireless communication systems has likely lead to a continuing development of single use hardware and software dedicated to multiple TDMA formats. As demand for TDMA wireless communication grows, the need to mitigate multipath interference also grows, as does the costly demands of supporting single use hardware and software in multiple TDMA formats.
Accordingly, there is a need for achieving the benefits of diversity reception through a common system, method, and program whereby one or more frequencies are transmitted or received by one or more antennas selected by a single routine. The system, method, and program must be adaptable to the dynamic frequencies of uplink and downlink channels integrated in time or separated in frequency and seamlessly integrate a multiple quality assessment of signal quality that effectively discriminates against multipath interference.
A system, method, and program for selecting an antenna from a plurality of antennas in a wireless communication system having a dynamic frequency range is disclosed. This disclosure describes how a singular quality indicator derived from a plurality of quality parameters improves diversity selections in uplink or downlink channels integrated in time or separated in frequency. The quality indicator is derived in part from a synchronization, a cyclical redundancy check, and a differential receive signal strength indicator process. The processes modify a quality indicator when a sync error, a cyclical redundancy check error, or one of a number of receive signal strength conditions is detected. When a predetermined quality threshold exceeds the quality indicator at any point in time, antenna selection occurs.